trains in Europe usually have a different price depending by the speed. In Italy there are 3 categories: the slow trains (inter-regionals, direct, express) that do not require a supplement, the fast trains (intercity, eurocity) that require a supplement and a reservation can be done, and the very fast trains (eurostars aka pendolino = tgv in France, ...) that over the supplement do require a reservation.

Your pass already include the supplement, so you don't have to worry about it. And depending by the train you wanna catch, you'll have to see if the reservation is required or not. Sometimes (on busy days and times) the reservation can be highly required, BTW you may want to know that 20% of the seats are always kept unreserved on IC and EC, so if you catch your train from the origin station you may be able to find plenty of seats going a bit earlier (you will find some label on the compartment doors saying wich seat-numbers are reserved).

About the reservation fee, those prices you wrote are absolutely absurd. Probably they are applied by raileurope for online reservations and other services, but you should know that you can reserve a seat up to 5 hours before the train departure (from its origin station, not from yours) for just 5000 lire (about 3 American dollars) a person for IC and EC, 20 minutes before the departure for a bit higher price for Eurostars (it includes the supplement for us, but you should have a lower price having the supplement already paid).

Hope this helps. Ciao Flavio in Rome